From BlenderWiki

Edit Methods

Here you can specify the details for the workings of certain editing commands like duplication (Duplicate with object). You can also change the amount of undo steps and whether the undo should work globally or locally, see the Undo and Redo page.

Add new objects group

Enable Switch to Edit Mode if you want Blender to automatically go into Edit mode when you add an object.

Enable Aligned to View and, when new objects are added, they will be automatically rotated to face the view you are in. Otherwise, they will be global axis-aligned (i.e. always have null rotations).

Auto key framing for animation is also partly controlled from here, see the timeline page of the Animation chapter for more details.

Auto Save

This part is tackled in the undo and redo page later on in this chapter.